Include a calcium-phosphorus source in the grain mix at 1 to 2 percent.

Formulating rations allows you to feed your animals efficiently. It provides animals a reasonable amount of food containing all the nutrients they need. You can formulate a ration with the help of a computer or by hand. A computer analysis can provide a more complete nutrient profile and include economics.

Expressing computer ration information

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A ration analysis reviews the nutrients all of the feeds add to the ration. It doesn’t balance the ration, and thus doesn’t correct any nutrient deficiencies or excesses. For an accurate analysis, you must know how much of each feed you give including the nutrient content.

A ration balancer program combines feeds to meet the nutrient needs set for a ration. The nutrient content of the feed determines how much you feed to meet your herd’s needs. A balancer program doesn’t consider feed costs or profit.

Least cost formulation includes:

Defining the nutrient needs or constraints for the ration.

Finding what feeds need combining to meet or exceed these constraints at the lowest cost per pound of dry matter (DM).

Least cost formulations change as feed costs change. The computer will often give an opportunity or break-even cost for feeds not used in the ration. It’s thought to be a good buy when the price of an unused feed goes below the opportunity price. In this case, reformulate the ration to see how much of that feed you can now use.

A true maximum profit ration program includes:

A least cost function

Milk price information

A maximum profit (income over feed cost) for one of the constraints or specifications to formulate on

In maximum profit, the computer selects feeds and a milk production level to obtain maximum profit. In least cost or balanced rations, the computer only selects feeds to meet the nutrient needs specified for a given level of milk production.

Rules of thumb for formulating lactating cow rations

Know the dry matter intake of your lactating cows. Use table 1 as a guide.

Acid and neutral detergent fiber content

Neutral detergent fiber (NDF) should be at least 28 percent of the ration DM. Forages should account for 75 percent or more of the total ration NDF (1.2 percent of body weight or 21 percent of ration DM).

Protein and nonprotein nitrogen

Make sure the ration meets the cows’ protein needs (16 to 18 percent in early lactation rations). A low rumen degradable protein source may be good in early lactation rations for high producing cows.

Limit urea to 0.4 pounds per cow daily. Don’t feed more than 0.2 pounds daily to cows in phase 1 and 2.

Fat

Total fat should not go above 7 percent of the diet DM. No more than 2 percent added fat should be from any one of these sources: animal, vegetable or rumen inert.

When feeding fat, increase the following in the ration DM.

Calcium to 0.9 to 1 percent

Magnesium to 0.3 percent

ADF to 20 percent or more

Minerals and vitamins

Salt should be included in the grain mix at 1 percent. Another option is feeding salt at the daily rate. Individual cows need 1 ounce for maintenance plus 1 ounce for every 30 pounds of milk.

A calcium-phosphorus mineral source should be included in the grain mix at 1 to 2 percent. Another option is feeding these minerals near a rate of 1 ounce per 10 pounds of milk.

Supplement vitamins (A, D and E) and trace minerals in the ration to meet the cows’ needs.

James Linn, former UMN Extension animal scientist -dairy nutrition; Michael Hutjens, University of Illinois; Randy Shaver, University of Wisconsin; Donald Otterby, College of Food, Agriculture and Natural Resource Sciences; W. Terry Howard, University of Wisconsin and Lee Kilmer, Iowa State University